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|
;; NOTE: automatically generated by the build system.
.include "../config/generated.s"
.segment "HEADER"
;; Bytes 0-3: NES\0 magic header.
.byte 'N', 'E', 'S', $1A
;; Standard 32KB + 8KB NROM cartridge.
.byte $02, $01
;; Horizontal mirroring, no battery.
.byte $00
;; We use the NES 2.0 header mainly to differentiate between NTSC vs PAL in
;; a way that emulators won't ignore it.
.byte $08
;; Blanked out stuff.
.res $04, $00
;; NTSC vs PAL
.ifdef PAL
.byte $01
.else
.byte $00
.endif
;; Blanked out stuff.
.res $03, $00
.segment "CODE"
.include "../include/apu.s"
.include "../include/oam.s"
.include "../include/ppu.s"
.include "../include/asm.s"
.include "../include/joypad.s"
.include "../include/globals.s"
.include "assets.s"
.include "background.s"
.include "player.s"
.include "title.s"
.include "driver.s"
.include "vectors.s"
.proc main
;; Disable the PPU and zero out variables which shadow PPU registers.
lda #0
sta PPU::MASK
sta PPU::zp_mask
sta PPU::zp_control
;; Initialize other global variables which the rest of the game assume to
;; have zero as their initial values.
sta Globals::zp_flags
sta Joypad::zp_buttons1
sta Joypad::zp_buttons2
;; Initialize the assets for the game.
jsr Assets::init
;; Initialize some PAL-specific constants.
.ifdef PAL
lda #0
sta Driver::zp_pal_counter
.endif
;; We shadow the PPU control register in memory. Depending on the `make`
;; target we might need to switch directly to the main game. Otherwise we go
;; into the title as expected.
.ifdef PARTIAL
jsr Driver::switch
lda PPU::zp_control
sta PPU::CONTROL
.else
jsr Title::init
lda #%10001000
sta PPU::zp_control
sta PPU::CONTROL
.endif
cli
;; Enable back the PPU
lda #%00011110
sta PPU::zp_mask
sta PPU::MASK
@main_game_loop:
READ_JOYPAD1
lda Globals::zp_flags
and #%00000011
beq @title_screen
cmp #1
beq @game_screen
jmp @over
@title_screen:
;; If we are in a transitioning state, avoid the update from the title.
lda Globals::zp_flags
and #%00000100
bne @do_switch
jsr Title::update
beq @set_flags
@do_switch:
;; Start was pressed by the player, switch to the main game.
jsr Driver::switch
jmp @set_flags
@game_screen:
jsr Driver::update
;; NOTE: fallthrough
@set_flags:
lda #%10000000
ora Globals::zp_flags
sta Globals::zp_flags
@wait_for_render:
bit Globals::zp_flags
bmi @wait_for_render
;; Rendering is done, we can perform another iteration of the loop!
jmp @main_game_loop
@over:
;; TODO: allow to start over, reset flags, control register, etc.
jmp @over
.endproc
|
